The detection and measurement of pathogenic bacteria is an extremely important function in the diagnosis of disease, evaluation of contamination of the environment and foods, and in epidemiological surveillance. We have developed an assay amplification system which can be used to detect the antigens and DNA specific for infectious organisms at very low concentrations, and to report the results in a color-test format. In this proposal, we suggest that we will use this system for the measurement of several Salmonella species (Salmonella typhi, Salmonella paratyphi A) and the SLT (shiga-like toxin)-producing Escherichia coli strains especially E. coli O157/H7. The approach to be used is to develop ELISA assays based on the known specific antigens of these bacteria and DNA hybridization assays based on characteristic sequences for Salmonella sp in general (invA-invE), for Salmonella typhi and Salmonella paratyphi A (tyvelose synthetase gen) and for SLT-I and SLT-II genes. These tools will be assembled in protocols useful in evaluating patients thought to be infected with these organisms, including a new approach to amplify and recover viable bacteria from ELISA plates after detection. The protocols will be tested in a laboratory which routinely monitors the presence of infection by these organisms (in Bangalore, India) and compared with the results obtained using more traditional microbiological identification procedures. At the end of this effort, we would have produced a relatively inexpensive approach which would permit the application of this technology to the identification of infectious organisms, and in the Phase II effort we would extend the range of infectious organisms which could be measured using this technology. PROPOSED COMMERCIAL APPLICATION Detection of specific pathogens is an important component of disease detection, food safety and epidemiological surveillance. If the technology developed in this work results in the production of convenient, field-deployable kits for the detection of these pathogens, they will be widely used.